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Subject[PATCH 1/3] MIPS,bpf: Fix using smp_processor_id() in preemptible splat.
Date
If the kernel is configured with preemption enabled we were getting
warning stack traces for use of current_cpu_type().

Fix by moving the test between preempt_disable()/preempt_enable() and
caching the results of the CPU type tests for use during code
generation.

Signed-off-by: David Daney <david.daney@cavium.com>
---
arch/mips/net/ebpf_jit.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c
index 3f87b96..721216b 100644
--- a/arch/mips/net/ebpf_jit.c
+++ b/arch/mips/net/ebpf_jit.c
@@ -113,6 +113,7 @@ struct jit_ctx {
u64 *reg_val_types;
unsigned int long_b_conversion:1;
unsigned int gen_b_offsets:1;
+ unsigned int use_bbit_insns:1;
};

static void set_reg_val_type(u64 *rvt, int reg, enum reg_val_type type)
@@ -655,19 +656,6 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx)
return build_int_epilogue(ctx, MIPS_R_T9);
}

-static bool use_bbit_insns(void)
-{
- switch (current_cpu_type()) {
- case CPU_CAVIUM_OCTEON:
- case CPU_CAVIUM_OCTEON_PLUS:
- case CPU_CAVIUM_OCTEON2:
- case CPU_CAVIUM_OCTEON3:
- return true;
- default:
- return false;
- }
-}
-
static bool is_bad_offset(int b_off)
{
return b_off > 0x1ffff || b_off < -0x20000;
@@ -1198,7 +1186,7 @@ static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
if (dst < 0)
return dst;

- if (use_bbit_insns() && hweight32((u32)insn->imm) == 1) {
+ if (ctx->use_bbit_insns && hweight32((u32)insn->imm) == 1) {
if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
b_off = b_imm(exit_idx, ctx);
if (is_bad_offset(b_off))
@@ -1853,6 +1841,18 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)

memset(&ctx, 0, sizeof(ctx));

+ preempt_disable();
+ switch (current_cpu_type()) {
+ case CPU_CAVIUM_OCTEON:
+ case CPU_CAVIUM_OCTEON_PLUS:
+ case CPU_CAVIUM_OCTEON2:
+ case CPU_CAVIUM_OCTEON3:
+ ctx.use_bbit_insns = 1;
+ default:
+ ctx.use_bbit_insns = 0;
+ }
+ preempt_enable();
+
ctx.offsets = kcalloc(prog->len + 1, sizeof(*ctx.offsets), GFP_KERNEL);
if (ctx.offsets == NULL)
goto out_err;
--
2.9.5
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